The present invention relates to a testing apparatus or diagnostic device suitable for use in diagnosing disorders in humans or lower mammal subjects. In particular the present invention is directed towards a testing apparatus suitable for diagnosis of gastrointestinal disorders by detection of the urease enzyme.
Helicobacter pylori (H. pylori) has been implicated in causing chronic histological gastritis. Its causal role in peptic ulceration is also apparent, but less clear in relation to non-ulcer dyspepsia. The role of H. pylori can be more effectively controlled if a quick, inexpensive testing apparatus for detecting it is used. Upon detection or exclusion of H. pylori, therapeutic options can be effected to eradicate the infection or treat the symptoms if the infection is excluded.
As with the management of any disorder, the rapid, precise, and accurate diagnosis of gastrointestinal disorders is of paramount importance. However, the diagnostic methods typically employed in the art, such as histopathology, are often slow, cumbersome, costly and may yield equivocal or inaccurate results.
Helicobacter pylori can be detected by blood test for antibodies. However, the blood test can remain positive for many months after the bacteria have been eradicated so that checking a patient""s success in eradicating the bacteria is not possible. Furthermore, the presence of antibodies presents a falsely positive result in approximately 10 to 15% of patients due to cross reaction with other antibodies.
Other methods for detecting H. pylori include the 13C and 14C breath tests. These test require the availability of the expensive isotopes 13C and 14C together with the expertise to carry out the test and the ability to detect the presence of 13C and 14C using very expensive equipment. This includes gas chromatography or a scintillation counterxe2x80x94both are expensive pieces of equipment. Hence, the direct detection of active Helicobacter pylori infection to date has been difficult to achieve unless one can obtain tissue from the stomach.
It is known that gastrointestinal disorders of the upper gastrointestinal tract may be detected and diagnosed by methods and compositions for the detection of urease enzyme in the gastric mucosa or gastric fluid of humans or lower animals. U.S. Pat. No. 4,748,113 (Marshall) describes a test kit for urease enzyme detection. However, this test kit is bulky and requires storage at 2-8xc2x0 C.
A further test method and kit known as PYLORITEK(trademark) described and claimed in U.S. Pat. Nos. 5,314,804 and 5,420,016 utilises a number of components, such as a test pad incorporating a diffusion element, a reaction chamber and hydration solution. This test kit is also bulky, requires storage at 2-7xc2x0 C. and not simple to use.
The bulkiness and necessity to refrigerate the above mentioned kits adds expense to the storage and shipping of such kits.
It has been found that the aforesaid limitations of the known kits have imposed limitations on the extent of use of such kits, particularly in environments where storage and shipping is a problem, and an object of the invention is to alleviate that situation.
The present invention overcomes the disadvantage associated with the necessary refrigeration of the prior art testing kits, by providing a testing apparatus having a dry indicating composition responsive to urease. The present invention resides in the appreciation that a dry indicating composition responsive to urease may be used, and that the moisture content required for the test to take place may be provided by the gastric material sample being tested.
In a first aspect the present invention consists in a testing apparatus for detecting urease in a gastric material taken from a mammal, said apparatus comprising a dry indicating composition responsive to said urease, a backing sheet supporting said dry indicating composition, a cover sheet sealingly adhered about is periphery to said backing sheet to enclose said dry indicating composition, wherein at least one of said backing sheet or said cover sheet has a transparent portion in alignment with said dry indicating composition, and wherein said cover sheet may be peeled from said backing sheet and resealed therewith wherein said testing apparatus can be stored a room temperature.
Preferably said dry indicating composition is absorbed or impregnated into or applied to said backing sheet, or alternatively absorbed or impregnated into or applied to wafer adhered to said backing sheet.
Preferably said wafer or backing sheet to which said dry indicating composition is absorbed or impregnated is of suitable thickness to provide sufficient buffering capacity to neutralize acid present in said gastric material.
Preferably said wafer or backing sheet to which said dry indicating composition is absorbed or impregnated comprises a paper having a weight of at least 70 gsm, more preferably about 90 gsm.
Preferably the dry indicating composition prior to drying comprises a liquid composition of:
(a) urea;
(b) an indicator having a pKa of from about 6.5 to about 8.5 at an effective concentration; and
said liquid composition has a pH from about 5.0 to about 6.5, being at least about one pH unit lower than the pKa of said indicator.
Preferably said indicator is present at a concentration of 2 to about 100 milligrams per liter.
Preferably said indicator is one of p-nitrophenol, bromothymol blue, phenol-red, neutral red, quinoline blue, cresol purple and thymol blue.
In a second aspect the present invention consists in a method for detection of a gastrointestinal disorder in a mammal by detection of urease in gastric material of the mammal, comprising the steps of:
(a) obtaining a sample of gastric material from said mammal;
(b) providing a day indicating composition of a testing apparatus for detecting urease in a gastric material taken from a mammal, said apparatus comprising a dry indicating composition responsive to said urease, a backing sheet supporting said dry indicating composition, a cover sheet sealingly adherent about its periphery to said backing sheet to enclose said dry indicating composition, wherein at least one of said backing sheet or said cover sheet has a transparent portion in alignment with said dry indicating composition, and wherein said cover sheet may be peeled from said backing sheet and resealed therewith wherein said testing apparatus can be stored at room temperature; and
(c) observing the color of said composition; wherein a change of color of said composition indicates the presence of urease and the existence of a gastrointestinal disorder in the mammal.
In a further aspect the present invention consists in a method for detection of a gastrointestinal disorder in a mammal by detection of urease in gastric material of the mammal, comprising the steps of:
(a) obtaining a sample of gastric material from said subject;
(b) providing a dry indicating composition sealed under a transparent cover, in which prior to drying, said composition comprises:
(i) urea; and
(ii) as indicator having a pHa of from about 5.0 to about 8.5 at an effective concentration;
said composition prior to drying having a pH from about 5.0 to about 6.5, the pH of said composition is at least about one pH unit lower than the pKa of said indicator;
(c) storing said dry indicating composition at room temperature;
(d) unsealing the transparent cover;
(e) contacting said sample with said dry indicating composition;
(f) re-sealing the transparent cover; and
(g) observing the color of said composition; wherein a change of color of said composition indicates the presence of urease and the existence of a gastrointestinal disorder in the mammal.
Preferably in step (e) said sample of gastric material is applied to one side of a wafer or backing sheet to which said dry indicating composition is absorbed or impregnated, following which said sample permeates said wafer or backing sheet, and in step (g) said color is observed by viewing the opposite side of said wafer or backing sheet to that on which said sample was applied.